Echinococcus (Echinococcosis) and Versteria (Versteriosis) – Antibody, Microscopy, and PCR

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Background
This document provides antibody (serology), microscopy, and PCR testing information for echinococcosis and versteriosis (also known as Versteria cysticercosis) at Public Health Ontario (PHO). The causative agent of echinococcosis is the parasitic larval cestode Echinococcus. The causative agent of versteriosis is the related parasitic larval cestode Versteria.

Cystic echinococcosis (CE), also known as hydatid disease, is primarily acquired through ingestion of Echinococcus eggs originating from canid feces. It usually causes a confined, unilocular fluid-filled cystic lesion that grows slowly over multiple years. CE mainly associated with E. granulosus complex (includes E. granulosus sensu stricto, E. equinus, E. ortleppi, and E. canadensis) and, less commonly, E. oligarthrus.

Alveolar echinococcosis (AE) is also primarily acquired through ingestion of Echinococcus eggs from canid feces but usually causes an invasive, irregularly multilocular fluid-filled and/or solid tumor-like lesion that grows over multiple months to years. It is mainly associated with E. multilocularis and, less commonly, E. vogeli.

Versteriosis is primarily acquired through ingestion of Versteria eggs from mustelid feces and causes similar invasive lesion(s) as AE, but is predominantly reported in individuals with an impaired immune system.

Updates

Updated to consolidate microscopy and serology testing information into a single testing information webpage.

* Copie d'impression non contrôlée. Valide uniquement le jour de l'impression : 19 oct. 2026.

Testing Indications

Serology is advised for individuals with compatible exposure history and clinical presentation for AE, CE, or versteriosis. Microscopy and PCR on body fluid or tissue samples (e.g. cyst aspirate) can also be considered if available to collect safely, although imaging along with serology may be sufficient for diagnosis in most cases. For AE and versteriosis, histopathology may provide additional diagnostic support but is not available at PHO.^1,2

AE is a Disease of Public Health Significance (DOPHS) under the Health Protection and Promotion Act (HPPA). Additional testing and management recommendations are stated in the Ontario Ministry of Health Infectious Disease Protocol Appendix 1 for Disease: Echinococcus multilocularis infection.

Acceptance/Rejection Criteria

Serology will only be performed if any of the following clinical criterion is documented on the requisition form:

Lesion(s) on imaging (e.g. cyst) suggestive of echinococcosis or versteriosis
Exposure to a confirmed animal case (e.g. infected dog) of echinococcosis or versteriosis

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
Echinococcus granulosus - Antibody	General Test Requisition	Serum	5.0 ml blood or 1.0 ml serum	Blood, clotted – vacutainer tubes (SST)
Echinococcus multilocularis - Antibody	General Test Requisition	Serum	5.0 ml blood or 1.0 ml serum	Blood, clotted – vacutainer tubes (SST)
Versteria - Antibody	General Test Requisition	Serum	5.0 ml blood or 1.0 ml serum	Blood, clotted – vacutainer tubes (SST)
Echinococcus or Versteria - Microscopy	General Test Requisition	Body fluid or tissue specimens (e.g. aspirates, biopsies)	1 ml (fluid) or 0.2 g (tissue)	Sterile container
Echinococcus - PCR	General Test Requisition	Body fluid or tissue specimens (e.g. aspirates, biopsies)	1 ml (fluid) or 0.2 g (tissue)	Sterile container

Submission and Collection Notes

Complete all fields of the requisition form.

Important: Specify any of the following testing indication on the requisition. Failure to provide this information may result in rejection:

Lesion(s) on imaging
Exposure to a confirmed animal case

Where known, specify whether the patient is suspected of cystic (E. granulosus) or alveolar (E. multilocularis) echinococcosis,as the type of test may differ.

Label the specimen container(s) with the patient’s first and last name, date of collection, and one other unique identifier such as the patient’s date of birth or Health Card Number. For additional information see: Criteria for Acceptance of Patient Specimens. Failure to provide this information may result in rejection or testing delay.

Limitations

For serology: Grossly haemolysed, lipemic, contaminated specimens, and specimens containing anti-coagulant are unsuitable for testing.

Storage and Transport

For serology: Centrifuge tube if using serum separator tube (SST).

Place specimen container in a biohazard bag and properly seal the bag.

Specimens should be stored at 2-8°C and shipped on ice packs to PHO as soon as possible. All clinical specimens must be shipped in accordance to the Canadian Transportation of Dangerous Good Act.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Echinococcus antibody testing is referred out to the National Reference Centre for Parasitology (NRCP) in Montreal. Turnaround time is up to 30 calendar days from receipt at PHO.

Echinococcus and Versteria microscopy is performed daily from Monday to Friday at PHO’s Toronto site. Turnaround time for microscopy is up to 5 calendar days from receipt at PHO.

Echinococcus PCR testing is referred out to National Reference Centre for Parasitology (NRCP) in Montreal. Turnaround time is up to 42 calendar days from receipt at PHO.

Test Methods

Echinococcus genus-level serology is performed at the NRCP using an indirect enzyme-linked immunosorbent assay (ELISA) based on non-specific E. granulosus hydatid fluid soluble antigens (EgHF). Additional species-level serology to differentiate E. granulosus from E. multilocularis is also performed at the NRCP using an immunoblot panel based on specific recombinant E. multilocularis Em18 (recEm18) and Em95 (recEm95) antigens (Sako Y et al., J Clin Microbiol 2002).³ Echinococcus and Versteria microscopy is performed at PHO using direct wet mount and acid-fast staining. Echinococcus PCR is performed in Alberta using a laboratory-developed multiplex assay targeting the E. granulosus cox gene and E. multilocularis nad2 gene (Santa MA et al., Int J Parasitol Parasites Wildl 2018).⁴

There is currently no specific test available at PHO for Echinococcus oligarthrus, Echinoccocus vogeli, and Versteria, however case reports suggest potential cross-reactivity with the Echinococcus genus-level ELISA described above. Cross-reactivity with Taenia solum serology has also been reported.

Performance and Limitations
Echinococcus EgHF ELISA performance has been primarily studied for E. granulosus hepatic cysts, with reported sensitivity of 75-85% for CE1 cysts, 85-97% for CE2 or CE3 cysts, and 30-60% for CE4 or CE5 cysts. Sensitivity decreases to 50 to 60% for E. granulosus pulmonary cysts. Sensitivity for other isolated cyst locations is not well established and varies depending on reported case series, e.g. 40-90% for E. granulosus splenic cysts. For E. multilocularis, the sensitivity of EgHF ELISA has been reported between 80-95% based on lesion viability and treatment, and may be as low as 30% for calcified, nonviable lesions. Overall sensitivity may be affected by immunosuppression. Overall specificity has been reported between 85-90%, with cross-reactivity with other helminths including Taenia, Schistosoma, Strongyloides, and filarial nematodes. Cross-reactivity may also be seen in the context of malignancies, pregnancy, and autoimmune diseases. The assay may cross-react with other Echinococcus species and Versteria, but the extent cross-reactivity is not well established. This assay does not distinguish between species. The EgHF ELISA may remain positive for years after therapy and may not be able to distinguish between active, resolved, or recurrent infection.^5-11

Echinococcus multilocularis species-level recEm18 and recEm95 immunoblot testing is reported by NRCP to have 93% sensitivity for active infection and 100% specificity based on limited data. Performance may be affected by immunosuppression or treatment. A negative immublot result, in the context of a positive EgHF ELISA, would suggest likely infection with Echinococcus granulosus in 80-95% of cases, however infection with other Echinococcus species or Versteria cannot be ruled out. The assay is expected to be negative for nonviable lesions and may indicated cure following treatment, however negativization may takes multiple years.^11-14

Microscopy sensitivity on cyst material for CE is variable depending on cyst size, viability, and treatment course. For AE and versteriosis, direct specimen microscopy is rarely positive due to the excentric tissue invasion as opposed to concentric fluid collection usually seen in CE. In those invasive AE and versteriosis cases, histopathology would better support the diagnosis if available locally. ^15-16

PCR sensitivity on cyst material for CE and AE ranges from 50-95%, based primarily on animal studies. Sensitivity may vary by intraspecies genotypes. Specificity is high and cross-reactivity between E. granulosus and E. multilocularis is not expected, but cross-reactivity with other Echinococcus species and Versteria is not known.^17-23

Algorithm

If a serology request meets the acceptance criteria listed above and has a request specifically for Echinococcus multilocularis, the Echinococcus genus-level ELISA will be performed first and if positive, the E. multilocularis immunoblot test will be automatically performed to confirm the species identification.

If body fluid or tissue samples (e.g. cyst aspirates) are submitted, microscopy will be performed routinely; PCR will only be added if specifically requested.

Interpretation

For Echinoccocus genus-level ELISA at NRCP (“Echinococcus by EIA – Referred out”):

Echinococcosis (pastoral) Sample Value	Result	Interpretation
≥ 1.20	High Positive	Echinococcus antibodies detected. Does not distinguish between species. Cross-reactivity may occur with other infections. May not distinguish between active, resolved, or recurrent infection.
≥ 0.45 and < 1.20	Low Positive	Echinococcus antibodies detected. Does not distinguish between species. Cross-reactivity may occur with other infections. May not distinguish between active, resolved, or recurrent infection.
≥ 0.35 and < 0.45	Equivocal	Echinococcus antibody status inconclusive. Clinical/exposure correlation required and repeat testing may be considered if clinically indicated.
< 0.35	Negative	Echinococcus antibodies NOT detected. Does not rule out infection, especially for early, small, calcified, degenerative, or non-hepatic lesions.

For Echinococcus multilocularis species-level immunoblot at NRCP (“Echinococcus multilocularis – Referred Out”):

Echinococcosis Immunoblot	Interpretation
E. multilocularis	Echinococcus multilocularis antibodies detected.
E. granulosis [sic]	Echinococcus multilocularis antibodies NOT detected. ELISA seropositivity for this patient most likely represents Echinococcus granulosus infection but cannot rule out infection with other species such as E. oligarthrus and E. vogeli or other non-specific cross-reactivity with other infections.
Cancelled	Due to the negative ELISA test for this patient, further testing by immunoblot for species identification is not performed. Refer to the ELISA results for management.

For Echinococcus or Versteria microscopy at PHO:

Parasite Microscopy	Interpretation
Parasite(s) found: Echinococcus species	Unable to distinguish between species by microscopy.
Parasite(s) found: Taeniidae family	Atypical features for Echinococcus and may suggest infection by another related genus such as Versteria or Taenia. Clinical correlation required.
Parasite(s) NOT found	Does not rule out infection. Microscopy sensitivity varies by species, cyst size, and viability.

For Echinococcus PCR in Alberta (“Parasite Investigation – Referred Out”):

Echinococcus multilocularis (DNA) NAT	Echinococcus granulosis [sic](DNA) NAT	Interpretation
Detected	Not detected	Echinococcus multilocularis DNA present.
Not detected	Detected	Echinococcus granulosus DNA present.
Not detected	Not detected	Echinococcus multilocularis and E. granulosus DNA not present. PCR sensitivity varies and does not rule out infection.

Reporting

Results are reported to the ordering physician or authorized health care provider (General O. Reg 45/22, s.18) or submitter as indicated on the requisition.

Specimens that are positive for E. multilocularis are to be reported to the Medical Officer of Health as per the Ontario Health Protection and Promotion Act.

References

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